An official website of the United States government
Helium droplets are unique hosts for isolating diverse molecular ions for infrared spectroscopic experiments. Recently, it was found that electron impact ionization of ethylene clusters embedded in helium droplets produces diverse carbocations containing three and four carbon atoms, indicating effective ion–molecule reactions. In this work, similar experiments are reported but with the saturated hydrocarbon precursor of ethane. In distinction to ethylene, no characteristic bands of larger covalently bound carbocations were found, indicating inefficient ion–molecule reactions. Instead, the ionization in helium droplets leads to formation of weaker bound dimers, such as (C2H6)(C2H4)+, (C2H6)(C2H5)+, and (C2H6)(C2H6)+, as well as larger clusters containing several ethane molecules attached to C2H4+, C2H5+, and C2H6+ionic cores. The spectra of larger clusters resemble those for neutral, neat ethane clusters. This work shows the utility of the helium droplets to study small ionic clusters at ultra-low temperatures.
more »
« less
To form or not to form a reaction complex: exploring ion–molecule reactions between C3H4 isomers and Xe+ and O2+
Ion–molecule reactions are an essential contributor to the chemistry of a diverse range of environments. Here we study the effects of isomeric structure and ionic character on the ion–molecule reaction between C3H4isomers and Xe+and O2+ions.
more »
« less
- PAR ID:
- 10540804
- Publisher / Repository:
- The Royal Society of Chemistry
- Date Published:
- Journal Name:
- Faraday Discussions
- Volume:
- 251
- ISSN:
- 1359-6640
- Page Range / eLocation ID:
- 125 to 139
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Calcium dicarbide, CaC2, has been characterized at high resolution in the laboratory, and its main isotopologue,40CaC2, has been assigned to 14 rotational emission lines between 14 and 115 GHz, including 12 previously unassigned lines, in the expanding molecular envelope of the evolved carbon star IRC+10216. Aided by high-level quantum calculations and measurements of multiple isotopologues, CaC2is determined to be a T-shaped molecule with a highly ionic bond linking the metal atom to the C2unit, very similar in structure to isovalent magnesium dicarbide (MgC2). The excitation of CaC2is characterized by a very low rotational temperature of 5.8 ± 0.6 K and a kinetic temperature of 36 ± 16 K, similar to values derived for MgC2. On the assumption that the emission originates from a 30″ shell in IRC+10216, the column density of CaC2is (5.6 ± 1.7) × 1011cm−2. CaC2is only the second Ca-bearing molecule besides CaNC and only the second metal dicarbide besides MgC2identified in space. Owing to the similarity between the predicted ion–molecule chemistry of Ca and Mg, a comparison of the CaC2abundance with that of MgC2and related species permits empirical inferences about the radiative association–dissociative recombination processes postulated to yield metal-bearing molecules in IRC+10216 and similar objects.more » « less
-
Abstract 8‐Oxo‐2′‐deoxyguanosine (OG) is the most common DNA lesion. Notably, OG becomes more susceptible to oxidative damage than the undamaged nucleoside, forming mutagenic products in vivo. Herein the reactions of singlet O2with the radical cations of 8‐oxo‐2′‐deoxyguanosine (OG.+) and 9‐methyl‐8‐oxoguanine (9MOG.+) were investigated using ion‐molecule scattering mass spectrometry, from which barrierless, exothermic O2‐addition products were detected for both reaction systems. Corroborated by static reaction potential energy surface constructed using multi‐reference CASPT2 theory and molecular dynamics simulated in the presence of the reactants′ kinetic and internal energies, the C5‐terminal O2‐addition was pinpointed as the most probable reaction pathway. By elucidating the reaction mechanism, kinetics and dynamics, and reaction products and energetics, this work constitutes the first report unraveling the synergetic damage of OG by ionizing radiation and singlet O2.more » « less
-
In our experiment, a trace amount of an organic molecule (M = 1H-phenalen-1-one, 9-fluorenone, pyridine, or acridine) was seeded into a gas mix consisting of 3% O2 with a rare gas buffer (He or Ar) and then supersonically expanded. We excited the resulting molecular beam with ultraviolet light at either 355 nm (1H-phenalen-1-one, 9-fluorenone, or acridine) or 266 nm (pyridine) and used resonance enhanced multiphoton ionization (REMPI) spectroscopy to probe for formation of O2 in the a 1Δg state, 1O2. For all systems, the REMPI spectra demonstrates that ultraviolet excitation results in formation of 1O2 and the oxygen product is confirmed to be in the ground vibrational state and with an effective rotational temperature below 80 K. We then recorded the velocity map ion image of the 1O2 product. From the ion images we determined the center-of-mass translational energy distribution, P(ET), assuming photodissociation of a bimolecular M-O2 complex. We also report results from electronic structure calculations that allow for a determination of the M-O2 ground state binding energy. We use the complex binding energy, the energy to form 1O2, and the adiabatic triplet energy for each organic molecule to determine the available energy following photodissociation. For dissociation of a bimolecular complex, this available energy may be partitioned into either center-of-mass recoil or internal degrees of freedom of the organic moiety. We use the available energy to generate a Prior distribution, which predicts statistical energy partitioning during dissociation. For low available energies, less than 0.2 eV, we find the statistical prediction is in reasonable agreement with the experimental observations. However, at higher available energies the experimental distribution is biased to lower center-of-mass kinetic energies compared with the statistical prediction, which suggests the complex undergoes vibrational predissociation.more » « less
-
Abstract Anionic ancillary ligands play a critical role in the construction of rare earth (RE) metal complexes due to the large influence on the stability of the molecule and engendering emergent electronic properties that are of interest in a plethora of applications. Supporting ligands comprising oxygen donor atoms are highly pursued in RE chemistry owing to the high oxophilicity innate to these ions. The scarcely employed bis(acyl)phosphide (BAP) ligands feature oxygen coordination sites and contain a phosphide backbone rendering it attractive for RE‐coordination chemistry. Here, we integrate bis(mesitoyl)phosphide (mesBAP) as an ancillary ligand into REIIIchemistry to generate the first dinuclear trivalent RE complexes containing BAP ligands; [{mesBAP}2RE(THF)(μ‐Cl)]2(RE=Y, (1), Gd (2), and Dy (3); THF=tetrahydrofuran). Each RE center is ligated to two monoanionicmesBAP ligands, one THF molecule and one chloride ion. All three molecules were characterized through single‐crystal X‐ray diffraction,31P NMR, IR and UV‐Vis spectroscopy.31P,1H and13C NMR on the diamagnetic yttrium congener1confirm asymmetric ligand coordination. DFT calculations conducted on2provided insight into the electronic structure. The magnetic properties of2and3were investigated via SQUID magnetometry. The GdIIIions exhibit weak antiferromagnetic coupling, corroborated by DFT results.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d4fd00005f
